Sematech gives green light on immersion lithography

SAN JOSE, Calif.  During a seminar on Friday (July 11), International Sematech here is expected to give the green light on the development of a new and radical chip-manufacturing technology called immersion lithography.

The Austin, Tex.-based chip-making consortium is expected to endorse immersion lithography and claim that there are no major barriers to enable the technology for advanced IC production. Sematech will report its findings at a seminar at the IBM Almaden Research Center in San Jose on Friday.

In immersion lithography, the space between the projection lens and the wafer in a tool is filled with a liquid. Immersion technology could offer better resolution enhancement and higher numerical apertures over conventional projection lithography.

Leading suppliers of lithography tools are initially looking to devise 193-nm scanners, equipped with immersion capabilities. The technology could extend 193-nm exposure tools to the 65-nm node and below, thereby pushing out 157-nm scanners, extreme ultraviolet (EUV), and other next-generation lithography (NGL) candidates.

While the immersion is promising, there are several hurdles. Polarization and microbubbles in the immersion process could potentially thwart the technology, according to analysts. And one major chip maker--Intel Corp.--remains skeptical, claiming the technology will not be ready in time for the 65- or 45-nm nodes.

Sematech, however, believes there are no major barriers with the technology. "It appears to be very promising," said Walter Trybula, a Senior Fellow at Sematech. "It appears to be engineering verses science," he said in an interview with SBN.

While Sematech has endorsed the technology, ASML Holding NV, Canon Inc. and Nikon Corp. are scrambling to develop 193-nm tools with immersion capabilities. The first "engineering tools" from vendors are expected to be released in mid-2004, according to Trybula.

The first production machines, with "super numerical apertures" (NAs), will not be ready for "two years," he said. The Sematech technologist was referring to high NAs of 1.0 and over. Today's 193-nm tools have high NAs in the 0.85 range.

Trybula acknowledged that there is still work to be done with immersion, but the current results are promising after a six-month investigation by the chip-making consortium.

Among the major issues are the fluid properties and the microbubbles. Researchers have demonstrated the ability to control liquid at 0.1 degree Celsius. "We've got that under control," he said.

The formation of microbubbles is also a concern. But Sematech found that the microbubbles in the immersion process were 3 to 10 microns in diameter, which would only reduce the lens contrast by only 3 percent, he said.

Sematech has also made substantial progress on the development of the liquid for immersion applications. The consortium found that "double de-ionized distilled de-gassed water" is a suitable liquid for immersion.